Probably as many variations on the theme as there are aircraft types.
One method is to have your essential services on a transfer bus that is powered by the main bus on the side in question. Power the non-essentials direct from the main bus
Then with a 'suitable arrangement of relays' (tm) arrange the transfer buses to become powered by the opposite sides main bus if their own main bus fails.
E.G. Gen 1 fails. Main AC bus 1 falls over. AC 1 transfer bus now fed by Gen 2. (Gen 2 continues to feed Main bus 2 and transfer bus 2).
This way you've load shed the non essentials and load transferred the essentials.
Hope that's of some use.
pb